OT: Earthing Systems USA

[Manglemender]

This isn't a PLC question but I knows that members of this forum have many and varied skills and experience.

Two of my current projects are bound for the USA. The customer for the first machine has advised me that they have a TN-S earthing system and also that the secondary of the supply transformer is Delta connected.

How does that work?
Is it likely to make use of a separate earthing transformer to make an artificial star point?
Is this common in the USA?

Thanks in advance,

Nick

 

[califflash]

I believe what they are referring to is that the protective earth and neutral of the equipment will be connected to separate wires which will then be grounded at the transformer or service entrance to the facility. This would differ from a TT system where the equipment would be grounded locally and a ground wire would not be provided.

You also need to ask if this will be a corner grounded or high leg delta system as you may need to do something with your drives, if any. A resistively grounded system may need special considerations also.

 

[James Mcquade]

you might get better results asking on an electrical website.

i am a member of this site (not trying to promote it).

www.mikeholt.com

regards,
james

 

[LadderLogic]

I also think that using the word "earthing" for what for ages has been called "grounding" is not the best idea.

Just a personal idiosyncrasy of mine.

 

[JRB]

Is it likely to make use of a separate earthing transformer to make an artificial star point? NO
Is this common in the USA? NO

 

[Lancie1]

Is it likely to make use of a separate earthing transformer to make an artificial star point?

It is more likely that your customer's Delta secondary is corner-grounded (cheaper and more common). This creates a dangerous situation where an unsuspecting electrician checks phase voltage to ground, and reads "0" and thinks the power is off.

 

[alittlethiny]

It is more likely that your customer's Delta secondary is corner-grounded (cheaper and more common). This creates a dangerous situation where an unsuspecting electrician checks phase voltage to ground, and reads "0" and thinks the power is off.

He might be talking about and ungrounded delta. Where there is no 277 potential. These places have ground detector lights and 480 volt lighting. The ground is just the building bonded to the service point or a concrete encased electrode.


or I could way the hell off?

 

[Lancie1]

He might be talking about an ungrounded delta.

If so, I would recommend that he cancel the contract, and run away as fast as he can go.

 

[Manglemender]

Thanks for the replies. Still waiting to hear from the customer what the actual situation is. I just hope it isn't corner grounded.

Nick